High altitude brush



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INVENTOR. WF Haai/@riz BY ab? MW/ United States Patent C HIGH ALTITUDE BRUSH Erle I. Shobert II, St. Marys, Pa., assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Appiication April 9, 1956, Serial No. 577,136

4 C laims. (Cl. 3110-228) This invention relates to carbon brushes for dynamoelectric machines that-aroused at high altitudes.

It iswell known that the carbonbrushes of electric motors and generators used in airplanesilying at high altitudes wear away very rapidly unless they are specially treated to prolong their usefulness. The brushes have been treated in various Ways to incorporate in them certain compounds, called adjuvants, that have been found to be etfective. Adjuvants that have been used include lithium carbonate, molybdenum disulfide, and many non-hydroscopic metallic halide salts. These adjuvants have been mixed with the basic carbon mixtures, they have been impregnated in the brushes, they have been coated onto the sides of the brushes and they have filled slots and laterally spaced openings in the brush faces.

All of these brushes, except the type mentioned last, will wear the adjoining commutator or slip ring uniformly, but they have the disadvantage that the adjuvants sometimes build up films on the current-collecting members that are so thick that they affect commutation adversely. This disadvantage is practically eliminated where the brush is provided with a plurality of laterally spaced cores of adjuvant, the ends of which are exposed at spaced intervals along the face of the brush. With such a brush, the portions between the cores are untreated and can therefore exert the influence of an untreated brush on machine performance because thick commutating films will not be built up in these untreated areas. Nevertheless, anotherdisadvantage arises, which is due to the difference in wear of the current-collecting ring because of the fact that the cores and the basic brush material do not have the same Wear characteristics. ln other words, grooves are worn around the ring. This unevenness of Wear can become so pronounced that in some cases it is unsafe to replace brushes without first machining the ring.

It is among the objects of this invention to provide a brush, which includes an adjuvant but which Wears the current-collecting ring uniformly without overfilming its surface.

Accordingly, the carbon body of the brush is provided with a plurality of substantially parallel openings which extend from the contact surface of the brush towards the opposite end of the brush. These openings are filled with the desired adjuvant. They are spaced apart in a direction across the width of the brush and are inclined in that direction. Consequently, as the brush Wears away, the areas of Contact of the inserts of adjuvant with the current-collecting ring will move across the ring, resulting in distributing the wear under the inserts and the intervening brush body over substantially the entire area of the ring.

The preferred embodiment of the invention is illustrated in the accompanying drawings7 in which Fig. l is a side view of my brush engaging a rotating current-collecting member, with one brush shown in secl10n;

2,370,353 Patented Jan. 20, 1959 ice Fig. 2-is a similar viewv after the brushes have been` worn considerably;

Figs. 3 and 4 are views of the contact face of a-brush as seen in Figs. 1 and 2, respectively; and

Fig. 5 is a perspective viewof a modification.

Referring to Figs. l and 3` of the drawing, a rotating current-collecting ring 1 is shown, which can be a slip ring or a commutator of a dynamoelectric machine. Engaging thisring is a pair of carbon brushes. These brushes will usually be just alike, so only one will be described. The body 2 of the brush is a rectangular block of carbon, the width of which generally is substantially coextensive with the width of the adjoining. ring.. They thickness of the brush ,circumferentially of the ring can be any desired amount, which is also true of the length or height of the brush. The body of the brush isprovided with two or more substantially parallel openings 3, which extend from its contact face outwardly toward its outer end. These openings are lled with the adjuvant 4 that it is desired to use in the brush. The particular adjuvant used is not important as far as this invention is concerned, but whatever material is used, it will tend to form a lm o-n the collecting ring and will wear the ring either more or less than does the rest of the brush. The brush openings, with their inserts of adjuvant, are spaced apart in a direction across the width of the brush; that is, the openings lie in a projected radial plane of the ring.

it is a feature of this invention that the openings and adjuvant inserts are not perpendicular to the surface of the adjoining collecting ring, but are inclined to it. They all lean in the same direction in the radial plane of the ring mentioned in the preceding paragraph. Consequently, as the brush wears away, the areas of contact of the adjuvant inserts with the ring will move across the ring because, as the inserts are shortened, their exposed ends recede from one end of the brush and approach the opposite end. This can be seen by comparing Figs. l and 3 with Figs. 2 and 4, which show the brush after it has been worn considerably. Due to this gradual shifting of the areas of contact between the adjuvant and the ring from one side of the ring toward the other side, grooves will not be worn in the ring. instead, the wear will progress slowly across the ring. It also will be reduced, because neither the inserts nor the brush body between them are permitted to continue their iniluence along only one band on the ring.

In order to distribute the wear nearly uniformly over substantially the entire area of the ring, the adjuvant inserts should be provided in such number and at such an inclination to the ring that, before the brush becomes worn so much as to have to be replaced, the area of Contact between each insert and the ring will have moved from its original position to a point where it will engage or overlap the area where the next insert originally engaged the ring. This can be done by inclining each insert at such an angle that its outer end will overlap the inner end of the next insert, as shown in Fig. l. ln other words, the inner end of each opening 3 or insert of adjuvant and the outer end of the opening beside it will both intersect a common transverse plane of the brush, which is perpendicular to the contact face of the brush.

It is not necessary that only the inner ends of the adjuvant inserts be exposed, for, as shown in Fig. 5, a side of each adjuvant-receiving opening 6 may be open so that the adjuvant 7 therein will be exposed. This happens when the openings are formed as slots in one or both sides of the brush body 8. The depth of the slots can be any desired amount, and they may even extend entirely through the brush.

According to the provisions of the patent statutes, I

have explained the principle of my invention and have Y illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A dynamoelectric brush having at one end a contact face`adaptedto engage a rotating current-collecting ring, the brush comprising a carbon body provided with a plurality of substantially parallel openings extending from said face toward the opposite end of the brush, and an adjuvant filling the openings, said openings being spaced apart in a direction across the width of the brush and being inclined in that direction; whereby, as the brush wears away, the areas of contact of said adjuvant with the current collecting ring will move across the ring.

2. A dynamoelectric brush having at one end a contact face adapted to engage a rotating current-collecting ring, the brush comprising a carbon body provided with a plurality of substantially parallel openings extending from said face toward the opposite end of the brush, and an 4 t adjuvant lling the openings, said openings being spaced apart in a direction across the width of the brush and being inclined in that direction to such an extent that the inner end of an opening and the outer end of the next opening will both intersect a common transverse plane of the brush perpendicular to said contact face; whereby, as the brush wears away, the areas of contact of said adjuvant with the current-collecting ring will move across the ring.

3. A brush according to claim 1, in which said openings are open only at said contact face.

4. A brush according to claim l, in which a side of each of said openings is open.

References Cited in the le of this patent UNITED STATES PATENTS 427,674 Daft May 13, 1890 2,736,830 Savage Feb. 28, 1956 FOREIGN PATENTS 115,704 Austria Jan. 10, 1930 646,778 Germany June 21, 1937 

